A pulmonary nodule is a common radiologic finding that represents a rounded opacity in the lung measuring up to 3 cm in diameter. Accurate ICD-10 coding for a Solitary pulmonary nodule is critical because it drives downstream clinical workflows—such as surveillance imaging, advanced diagnostic testing, or oncology referral—and determines payer coverage and reimbursement for those services.
For revenue cycle and compliance professionals, precise assignment of the correct diagnosis code ensures medical necessity is supported, reduces avoidable denials, and prevents inappropriate escalation to malignant neoplasm coding. This guide explains the ICD-10-CM code for Solitary pulmonary nodule, practical scenarios when to use the code, clear exclusions, related codes to consider, and actionable billing and documentation strategies to improve first-pass claims and audit readiness.
The ICD-10-CM Code for Solitary pulmonary nodule is R91.1.
A solitary pulmonary nodule is a single, discrete, well-circumscribed radiographic lung opacity up to 3 cm in diameter that is not associated with atelectasis, lymphadenopathy, or pleural effusion. In ICD-10-CM classification, R91.1 is used to report this nonspecific anatomic finding when documented as solitary; it does not imply benign or malignant etiology. Use of R91.1 indicates an imaging-detected nodule that requires diagnostic consideration, surveillance, or further workup but lacks definitive histopathologic or metastatic confirmation.
Use R91.1 when a chest CT identifies a single pulmonary nodule and the clinician documents it as a solitary pulmonary nodule without specifying etiology. This supports claims for diagnostic imaging, specialty consultation, and non-invasive follow-up planning.
Assign R91.1 for follow-up chest radiograph or CT when the encounter is explicitly for surveillance of a previously documented solitary pulmonary nodule and no new diagnosis or etiology is established. This distinguishes surveillance visits from encounters for confirmed neoplasm management.
Code R91.1 when the clinical encounter focuses on pre-procedural imaging review or risk assessment for a solitary pulmonary nodule before tissue diagnosis. It supports medical necessity for additional imaging, pulmonology evaluation, or image-guided biopsy planning.
Do not use R91.1 when biopsy or surgical pathology establishes cancer. Instead, report the appropriate malignant neoplasm code (for example, malignant neoplasm of bronchus and lung) because R91.1 is a nonspecific finding and would under-represent disease severity.
If the record documents multiple nodules or metastatic pulmonary nodules, R91.1 is inappropriate. Use codes reflecting secondary malignant neoplasm of lung or other specified conditions that capture multiplicity or metastatic origin.
Avoid R91.1 when the clinician documents a specific etiology—such as tuberculoma, fungal granuloma, or hamartoma. Assign the diagnosis code that reflects the specific infectious, inflammatory, or benign neoplastic condition instead of the nonspecific solitary nodule code.
| Condition | Code | When It Is Used | When It Is Not Used |
|---|---|---|---|
| Solitary pulmonary nodule | R91.1 | When a single, radiographically defined pulmonary opacity up to 3 cm is documented as solitary without histologic or etiologic confirmation | Not used when biopsy proves malignancy, when multiple nodules are present, or a specific cause is documented |
| Secondary malignant neoplasm of lung (metastatic pulmonary nodules) | C78.0 | When pulmonary nodules are documented as metastatic deposits from a known primary malignancy | Not used for solitary incidental nodules without evidence of metastasis or when a primary lung cancer is diagnosed |
| Other nonspecific abnormal finding of lung field | R91.8 | When the imaging shows an abnormal lung field finding that is not characterized as solitary or when the documentation lacks the specificity to call it solitary | Not used when documentation clearly identifies a solitary pulmonary nodule or when a specific diagnosis is available |
| Malignant neoplasm of bronchus and lung, unspecified | C34.90 | When pathology or clinical staging confirms primary lung malignancy and the encounter relates to confirmed neoplasm management | Not used for incidental solitary nodules without histologic confirmation or for metastatic pulmonary involvement from another primary |
Include exact nodule size (in mm), lobe and laterality, attenuation (solid, ground-glass), and growth compared with prior imaging. Payers evaluate medical necessity for surveillance and invasive procedures based on these specifics.
Document the reason for the visit (initial detection, surveillance interval), planned diagnostic steps (CT with contrast, PET-CT, biopsy), and expected timeframe. Linking the diagnostic plan to the nodule supports care necessity for ancillary services.
Ensure claims include R91.1 as primary or secondary diagnosis aligned with ordered services (imaging, biopsy, consult). Submit procedure notes or imaging reports when required by payer policies to reduce documentation requests and denials.
Leverage CombineHealth.ai’s AI-powered platform and its automated claim scrubbing and coding validation features to detect missing linkage between diagnosis and ordered tests, flag inconsistent laterality/diagnosis combinations, and recommend code adjustments prior to submission.
For image-guided biopsies or surgical resections, assemble imaging comparisons, multidisciplinary notes, and pathology requisitions to demonstrate medical necessity and justify advanced procedural CPT codes at the time of claim filing.
Coding for pulmonary nodule has direct impact on revenue cycle outcomes:
Accurate ICD-10 coding is critical for healthcare revenue cycle performance. CombineHealth.ai's AI-powered platform helps RCM teams ensure coding accuracy, reduce denials, and optimize reimbursement through intelligent denial management and claim validation. CombineHealth.ai's intelligent platform provides automated claim scrubbing and coding validation to catch errors before submission, reducing denials and improving first-pass acceptance rates.
Q1: What is the ICD-10 code for pulmonary nodule?
The ICD-10-CM code for pulmonary nodule is R91.1. This code applies when a single, radiographically identified lung opacity is documented as a solitary pulmonary nodule without biopsy confirmation of malignancy or specification of an alternative cause.
Q2: When should I use R91.1 vs related codes?
Use R91.1 for an isolated, undocumented solitary nodule. Use codes for secondary malignant neoplasm of lung when nodules represent metastases, and use malignant neoplasm codes when pathology confirms primary lung cancer. Use R91.8 when the finding is nonspecific or not described as solitary.
Q3: What documentation is required when coding for pulmonary nodule?
Document nodule size, anatomic location, imaging modality, comparison with prior studies, characterization (solid vs ground-glass), clinician assessment, and planned management. For procedures, also document indications, consent, and pre-procedural planning to support medical necessity.
Q4: What are common denial reasons when coding for pulmonary nodule?
Denials commonly stem from lack of specificity in documentation, billing R91.1 when malignancy is confirmed, or failing to link diagnostic codes to billed services. See our guide on denial management for strategies to reduce and resolve these denials.